Here is something I think is a decent idea:

When selecting your own collection, the search filter should only contain the manufacturers of the modules that you have added to your collection rather than the full list of all manufacturers. Having a more defined collection sort vs. entire library would make sense.

1U in 3U spaces to represent a converter?

I am thinking about adapting, but now realizing that this does not work unless you preemptively set the entire row.
I think a button to allow 1U to fit in top/mid/bottom of a 3U space would be amazing.